Bill Cheek - World Scanner Report

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RENEW BEFORE JUNE 30 AT
THE OLD RATES!

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CORRECTION

TO LAST MONTH’S PRICE
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WINDOWS 95

CLOSER TO RELEASE
AUGUST-’95

REFERENCE INFORMATION

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for free download from BBS or $5 fbrftoppy d&k •

A Journal ofySE-UHE Radio Technology & Engineering

111! f Pio^tlslied

Pul^lMifeer^Sdlters Check*

VolumeS, Number 4_ $5.0

Here’s a promise you wish we’d break.
So do we, but postal rate hikes and
drastic increases for paper and other
materials required to produce the WSR
force our promise to up the subscription
rates for the first time in history. It can’t
be helped, but I think you’ll agree we
held the line. So here’s the deal:

Effective July 1,1995, the new rates will
be etched into stone as follows:

Canada/

USA Foreign Surf

Single issue $ 5.00 $ 5.50

6-mos, 5-issues: $20.00 $25.00

1- yr; 10-issues: $35.00 $45.00

2- yr; 20-issues: $65.00 $75.00

Sorry, Hackers, but we have to do it or
dine at the local soup mission. We’ll
offer current subscribers the chance to

lock in the old rates for any of the three
regular periods of 6-mos, 1-yr, or 2-yrs.
Apologies to our Canadian and foreign
readers who have to bite more of the
bullet. Costs of postage, paper, and extra
handling have to be passed on to
everyone, pro-rata. When the new rates
go into effect, a discount is built in for
the longer sub periods.

AGA Associates informs me that they
are negotiating future volume purchases
of the Metex M-3850 and other Metex
multimeters and that our stated $179.95
price is not necessarily carved into stone.
Therefore, if you are interested in a
computer-interfaceable data acquisition
multimeter, give AGA Associates
another call or opportunity to present

Microsoft’s new operating system to
replace Windows 3.1 and Windows For
WorkGroups 3.11, formerly coded as
“Chicago” and now called Windows 95
seems solidly positioned for a long
awaited August, 1995, release.

I have been beta testing Windows 95
since the Spring of last year, and am

We remain committed to a program for
continual improvement, too. Suggestions
are welcome, of course, but barring
unforeseen circumstances or better
suggestions, we’re looking to upgrade
our laser printing facility from the
present 300-dpi to a 600/1200 dpi
workhorse. I’d like to hear from anyone
“in the business ” who might be able to
make us a good offer for the Cause.

Ultimate Scanner Book Price List

SPESi^

After Junei-30^:1995

USEuwfc

Engineering.:

their latest price and delivery quote:

AGA Associates
PO Box 99573
Seattle, WA 98199-0573
FAX (206) 217-9138

AGA Associates is a progressive,
forward thinking, new entry into the
hacker and hobby scene. You’ve
probably not heard of them before last
month, but unless I miss my guess, you’ll
see more and more of them in the
coming months. Their Metex
multimeters are hot performers and well
worth the hacker’s second look. I am
still ga-ga over their Windows
Scope View control program! Wow!

happy to report that I think it’s just about
ready. In fact, Microsoft has already
issued a “pre-release” version of
Windows 95 on a first-come, first-served
basis for $30. The “pre-release” is
designed for corporate and serious users
who need to plan ahead and cement their
computing needs in advance of purchase.

In case you didn’t know, Windows 95 is
an immensely improved graphical user
interface (GUI) over previous versions,
and just about eliminates the much
maligned MS-DOS operating system that
reigned supreme since 1980. Windows
95 comes with a better DOS than ever,
but if you are not a DOS lover, it is

04/23/95 ~ 23:30 - Page I

d * s*A■

.

possible that you’ll never have to deal
with a DOS command line and its
cryptic commands ever again! If you
are a DOS lover, then you may find
“hawg heaven ” with MS-DOS 7.0 that
comes with Windows 95 because you
can run “pure” DOS as ever, except with
as many simultaneous “windows” of
DOS as you like, within limits of reason.
Other operating systems such as prior
versions of Windows as well as OS/2
and certain enhancement programs such
as DesqView have always been able to
run multiple instances of DOS but Win
95 does it the best yet.

I mention Windows 95 now and will
periodically do so because a computer’s
operating system is extremely important
to the compleat scannist and hacker.
Win95 offers greatly improved on-and-
off-line communications, multitasking,
multithreading, stability, and power, and
at the same time, is easier to operate than
any of its predecessors and competitors.

If you are already into computers and
computing, you will want to give some
serious consideration to acquiring Win95
immediately upon release in August. If
you know nothing about computers now,
but may get one in the next few months,
be sure to wrangle a deal for Win95 on
that new computer. Don’t get stuck with
old MS-DOS and old Windows when the
hot new one is about to come down!

Windows 95 is specified by Microsoft to
run on 386DX or better computers, with
4-Mb RAM (min). One of my Win95
machines is a 386SX/16, however, where
it runs ok, albeit a little slow, but it
always did run slow. The required 4-Mb
minimum RAM is exactly that, a hard¬
core minimum, and the more RAM your
machine has, the better. Frankly, you’ll
want to consider 8-Mb as a “productive”
minimum from which to extract the
maximum performance that Windows 95
has to offer. If you can afford it, a 486 or
better computer is an ideal platform for
Win95. If you have a 386DX computer,
that will be ok, too. My kids each have a
386DX/33 on which Win95 runs just
fine. The single greatest factor that
impacts the performance of Win95, aside
from the type of computer, is RAM. 4-
Mb is minimum; 8-Mb best for most, and
16-Mb for heavy duty power users.

Here, let me show you a screenshot of my
desktop as I write this section. The
detail isn’t great because I had to shrink
down the image to conserve space, but
you get the idea. Gone are the days of
old Windows “program groups” and the
complexity of their installation.
Everything now runs mostly how you
want it to run. Yes, you get to choose!

I prefer to create an icon for most things
and to double-click them from the
desktop. There are several other ways,
one of which will suit most anyone.
Down at the lower left comer is a button
called START, from which you can do
anything, simple and easy like.

—I

Neither space nor topical dedication
allows me to pursue the subject of
Windows 95 much farther now. If future
interest warrants, I will dedicate a
column every other month or so to
Win95 topics simply because computing
and radio are welded together. Win95 is
a powerful tool for the compleat scannist
and hacker, and I would do a disservice
if I ignored it.

Radio is poised on the brink of major
change, and most of that change is
related to computers. Windows 95 is the
next generation operating system for the
downhill run into the 21 st century. It’s
pertinent. It’s relevant. Stay tuned. ©

■ = CONTEST RESULTS

Winners from last month’s contest are
still flowing in, so I’m not going to
announce them or the results until next
issue in the offhand chance this issue is
mailed before April 30, the contest’s
deadline. I’ve also decided to not
announce the names of the winners
unless they so request because of the
volatile nature of the contest. It occurred
to me that the target of my little contest
might vent some anger or other
retribution to the winners and I would
never knowingly direct that sort of thing
away from me onto anyone else.

Suffice it to say for now that people are
more attentive than I thought. The
comments from the winners so far have
been very heartwarming and interesting.
More on this next month.

Next issue (V5N5) will be the last for the
first half of 1995, and some subscriptions
will expire with that issue. You may want
to check your mail label for the expiration
date and renew early to lock in the old
rates and to lighten the load on Cindy who
makes sure everything about your account
is perfect You can renew for 6-mos, 1 -yr,
or 2*yrs, at the old rates, through June
30, 1995, so give it some thought, and
renew early to avoid missing an issue or
needlessly having to pay the higher rates
because you forgot!

04/23/95-23:30- The “World Scanner Report” © 1991-95; Volume 5, No 4; Page 2

RECEIVER SECTIONS

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IreES

PRO-2004/5/6 & PRO-2035

- Explained -

Continuing with our circuit analysis
series, this month we will take a look at
the main receiver sections of the PRO-
2004/5/6 and PRO-2035 series. The
PRO-43 will fit this analysis in some
ways, too. Schematics and circuit
symbols as shown will be for the PRO-
2006, but are readily related to the
PRO-2004, PRO-2005 and in some
instances, the PRO-43 because these
receivers share a lot of common
circuitiy.

The most critical section of any receiver
is its RF Front End, generally a
preamplifier with surge and spike
protection and highly desirable bandpass
filters. See last month for a detailed
analysis of the Bandpass Filter section of
these fine radios. We need not repeat it
here. But in summary, a signal enters
tlie receiver from the antenna jack and is
immediately sensed by DC shunt coil LI
and protection diodes, D1 & D2. Input
impedance of the receiver is established
by the adjustable L-2.

The RF signal then goes through the
ATTenuator switch, S-l, and on into the
bandpass filter network as discussed last
month.

Out of the bandpass filter network, the
RF signal goes into a precision designed,
wideband, low noise preamplifier
network consisting of transistors, Q3-Q5.
Q3 and Q4 are emitter followers.

primarily for impedance matching and
isolation of Q-5, the main gain amplifier,
from the antenna and B.P.F. networks.

Q3-Q5 are critically designed surface
mount transistors and should never be
tampered with by any but the most astute
hackers....and even then...????

Out of Q5, the highly amplified RF
signal goes into a little known circuit
that separates the men from the boys of
VHF-UHF scanners: a “doubly
balanced mixer”, or D.B.M. A real
class-act, the DBM is a superior device
or circuit that naturally eliminates
certain kinds of interference and
maintains a purity of its output signal.
The purpose of any mixer is to accept
two input frequencies and output a
single frequency. The outputs of most
frequency mixing processes are the sum,
the difference, and each of the two input
frequencies. Inferior mixers of the type
used in most scanners produce plenty of
other outputs as well, including phase
noise and harmonic modulation
products. The DBM is also a great
performer under strong signal
conditions that tend to overload lesser
mixers.

The DBM here consists of a special
sealed Schottky hot-carrier diode pack,
D30, and is balanced on both its inputs
and its output by L49 and L48. None of
these three components should ever be
tampered by the hacker.

PRQ-2006 RF FRONT END AND DBM

04/23/95-23:30 - The “World Scanner Report” © 1991 - 95 ; Volume 5 , No 4 ; Page 3

PRQ-2006 1st IF AMPLIFIER & 2nd MIXER

GES

Also inputted into the DBM is a local

one frequency. Read on, McDuff..

oscillator (LO) injection frequency from
tire PLL/VCO section. We’ll cover the
PLL and VCO at another time, but for
now, just know that the DBM gets two
inputs, one from the RF Front End, and
one from the LO. Obviously, the signal
from the RF Front End consists of ALL
frequencies between 25-1300 MHz
minus those above/below the Bandpass
Filter networks that are rejected: still,
there is a boatload of signals inputted to
tire DBM. The LO signal is a tuned
signal selected by the CPU based on the
frequency that appears in the Display.
Tire range of the LO is 636-1136 MHz
and 1368-1908 MHz, depending on the
frequency in the Display. The four
outputs of the DBM will consist of:

1. Sum of LO and RF ffeqs

2. Difference of LO and RFfreqs

3. LO frequency

4. RF frequency(ies)

Four outputs? That doesn’t sound
healthy, when you want to listen to just

The four distinct outputs of the DBM are
fed to narrowband amplifier, Q6, which
is tuned by resonant circuit, L52, to just
the narrow range of 607-612 MHz! This
has the effect of rejecting three of the
above four signals, leaving ONLY the
desired signal(s). Actually, a passband
of desired signals, but considerably
narrowed from the 25-1300 MHz
spectrum present at the antenna!

Sidenote: Getting the picture here yet?
A huge spectrum of signals comes into
the receiver via the antenna. The BPF
network rejects a lot of those signals,
especially those not in the band of
interest. (See last month). The RF
Amplifier amplifies what’s left; mixes it
with a frequency from the LO and feeds
four specific freqs or narrow bands of
freqs to the 1st IF amplifier, which
further narrows the range of signals that
can pass through.

The highly amplified, narrow range of
frequencies (607-612 MHz) that contain
the desired signal is fed to the 2nd
Mixer, Q7, a typical, single-ended
mixer of no special importance other
than, like the DBM, it has two inputs
and an output. The other input is a
second LO frequency from the
PLL/VCO section that’s selected by the
CPU based on the frequency in the
display. This injection frequency is a
single frequency between 559-563 MHz.

Like all mixers, the output of Q7
consists of four frequencies, sum,
difference, and each input frequency.
Once again, selectivity comes into play
by virtue of tuned device, T-l. Now we
get into the nitty gritty of receivers.
Consider:

Suppose the output of the 1st IF amp
were 611.5 MHz and that the LO was
563.0 MHz. Then the output of Q7
would be four frequencies:

1. Sum of LO and 1st IF freqs: 1174.5 MHz

2. Difference ofLO and 1st IF freqs: 48.5 MHz

3. LO frequency: 563.0 MHz

4. 1st IF frequency(ies): 611.5 MHz

Now see what happens if T1 is tuned to

48.5 MHz? The other three freqs are so
far off that they are totally rejected!

48.5 MHz is the output of T-l and is
then fed to one of two places, depending
on the Mode ( AM/NFM/WFM) setting.

If Mode is set to WFM, the 48.5 MHz
2nd IF signal is sent to 2nd IF amplifier
Q9, in the WFM section.

If Mode is set to NFM or AM, the 48.5
MHz 2nd IF signal is sent to 2nd IF
amplifier Q15, in the NFM/AM section.

Since the signal path goes into a “tee”,
one way or the other, we now have to
analyze each choice separately.

—

If Mode is set to WFM, the 48.5 MHz
2nd IF signal from Q7/T1 is sent to 2nd
IF amplifier Q9. Out of Q-9/T2, the

48.5 MHz signal goes straight into 3rd
Mixer, Qll, which mixes QlO’s 3rd LO
of 37.800 MHz, the four outputs of Qll
which are:

04/23/95 - 23:30 - The “World Scanner Report” © 1991-95; Volume 5, No 4; Page 4

1. Sum of LO and 2nd IF freqs: 86.30 MHz

2. Difference ofLOA 2nd IF freqs: 10.70 MHz

3. LO frequency: 37.80 MHz

4. 2nd IF ffequency(ies): 48.50 MHz

Qll feeds T3, which is tuned to 10.7
MHz, and which thereby rejects the other
three undesired signals.

Sidenote: Regardless of the signals in
the antenna, by the time the signal
leaves Q11/T3, it is a fixed 10.7 MHz
and does not change any further until it
has been processed by IC-1 into audible
signals.

The Q11/T3 signal goes into a highly
selective ceramic filter, CF-1, tuned to
10.7 MHz to further reject noise and
undesired signals. CF1 feed the 10.7
MHz 3rd IF signal into IC-1 at Pin 2
where it is internally processed, and
outputted at Pin 4 to go through CF2,
also tuned to 10.7 MHz, for more
rejection of undesired signals, and then
back into IC-1 at Pin 6 for final
processing into audible signals outputted
at Pin 10.

We will discuss what happens to audio
signals from Pin 10 in a future analysis
of peripheral and control circuits.

Both : If Mode is set to NFM or AM, the
48.5 MHz 2nd IF signal output of Q7/T1
is sent to a sharply tuned prefilter, XF1,
for rejection of undesired signals, and
then into 2nd IF amplifier Q15 & Q16.

Q16 feeds T7 for more tuning of 48.5
MHz and rejection of undesired signals
and then goes into IC2 at Pin 18.

An internal mixer in IC-2 at pin 18 feeds
by a 3rd LO signal from Pin 1 where
there is a 48.050 MHz quartz crystal.
The output of this 3rd Mixer is:

1. Sum of LO and 2nd IF freqs: 96.55 MHz

2. Difference of LO and 2nd IF freqs: 455 kHz

3. LO frequency: 48.05 MHz

4. 2nd IF frequency(ies): 48.50 MHz

The 455 kHz 3rd IF is internally
processed by IC2 and outputted at Pin 3
to sharply tuned ceramic filter, CF4, for
massive rejection of undesired signals.

The output of CF4 splits and goes two
ways, one back into IC2 at Pin 5 and the
other up to ceramic filter CF3, at the
input to the AM section. This “tee” path
is not a choice like that for WFM and

NFM/AM, though. Even when the
receiver is set to the NFM mode, a
portion of that 3rd IF signal goes
through the AM section of CF3, Q12 and
Q13, where an Automatic Gain Control
signal is developed by D33 for control of
the gain of the RF Front End. We will
discuss the AGC and other peripheral
receiver circuits at a later date. Just
remember for now that the AM section
of Q12 and Q13 is used for both AM and
NFM modes to generate the AGC signal.

Back to the “tee” at CF4, the other path
of which goes back into IC2 at Pin 5 for
final processing into audible signals
outputted at Pin 9. We will discuss what
happens to the audio signals from Pin 9
at a future time.

AM-onlv: If Mode is set to AM, the 455
kHz 3rd IF signal in IC2 is outputted at
Pin3 to and through CF4 for filtering
and rejection of undesired signals. The
output of CF4 splits (partly discussed
previously), one path back into IC2 at
Pin 5 and the other path to CF3 at the
input to AM section at Q12. CF3 is a
highly selective ceramic filter tuned to
455 kHz and which rejects undesired,
adjacent signals.

PRQ-2006 NFM/AM SECTION

4/24/95-1-.27PM- The “World Scanner Report” © 1991-95; Volume 5, No 4; Page 5

The 455 kHz output of CF3 is amplified
by Q12; timed by T5; amplified again by
Q13; tuned again by T6; then fed to
AM/AGC detector diode, D33, and
filtered into a varying DC (audio!) by
C160. The output of D33 splits, one
path going on to AGC control circuits (to
be discussed later) and the other path
through Automatic Noise Limiter diode,
D34. The output of D34 is an audio
signal. We will discuss what happens to
signals from D33 and D34 in a future
article on peripheral and control circuits.

Wfap-up

RF signals from the antenna are
prefiltered in the BandPass Filters;
amplified by Q3-5; mixed at D30 by a
local oscillator signal from PLL1 and
converted into the 1st Intermediate
Frequency of 607-612-MHz and
amplified by Q6. The 1st IF signal is
mixed in the 2nd Mixer by a 559-563
MHz LO signal from PLL2 and
converted into the 2nd IF frequency of
48.5 MHz and amplified by either Q9
(WFM) or Q15 (NFM/AM), depending
on tlie Mode setting of the receiver.

The WFM 2nd IF signal is mixed in Q11
by a 37.8 MHz signal from Q10, the
output of which is 10.7 MHz and fed to
the WFM chip, IC1 for final processing
into audio signals at Pin 10 of IC-1.

The NFM/AM 2nd IF signal is amplified
by Q15 & Q16 and fed to a mixer
internal to IC2 at Pin 18. The 48.05
mixing signal is generated by X2 and fed
into IC2 at Pin 1. where the internal 3rd
IF 455 kHz signal is produced,
amplified, and outputted to CF4 to Pin 3
of IC1. CF4 feeds the 455 kHz 3rd IF
back into IC1 at Pin 5, but also up to
CF3 for amplification byQ12&Q13.

NFM signals are processed by IC1 and
converted to audio at Pin 9. AM signals
are detected by D33 and noise limited by
D34 and fed to audio preamp, Q18.

NFM & AM Automatic Gain Control
(AGC) for the IF and RF amplifiers is
generated by D33 and distributed in a
path that will be discussed in a future
article. WFM mode does not use AGC.

Selectivity of the scanner’s WFM mode
is partly set by T3 and CF1 and polished
off to 150 kHz by CF2. The center of the
WFM Discriminator curse is set by T4
with the baseband & audio output at IC1,
Pin 10.

Selectivity of the NFM and AM modes is
partly set by XF1 and T7. CF4 shapes
the 15 kHz selectivity curve for NFM-
only signals and partly for AM signals.
AM selectivity is set at 6 kHz by CF3.
The center of the NFM Discriminator
curve is set by T8, with the baseband and
audio output at IC2, Pin 9.

The foregoing analysis is expressly for
the PRO-2006, but is matched almost
identically by the PRO-2005. The PRO-
2035 is a second close match except that
some of the circuit symbols differ from
that mentioned herein. As an example,
the DBM in the PRO-2035 is D31. The
PRO-2004 is also the subject of this
analysis, but there are a number of
design and circuit symbol differences
such that it may be difficult for the
neophyte to follow this discussion on a
PRO-2004 schematic.

For the PRO-2004, PRO-2005 and PRO-
2035, it is strongly suggested that you
have a schematic of the PRO-2006 to
hold up against the one for your scanner
so you can follow the discussion, and you
will, because these four radios are really
very much alike.

IF YOU NEED A SCHEMATIC diagram of the
PRO-2006 for this (or any other ) purpose, I will be
happy to prepare a nice one for you for a handling
fee of $5— plus a double stamped, self-addressed
envelope of your choice. The schematic consists of
two double-sided 11 x 17 sheets and one SVi x 11, so
at least send me a double-stamped #10 business
envelope with the five bucks. Note these are nicely
done schematics, so you may want to provide me with
a 9x12 manila envelope. If you don’t want to provide
the double postage and envelope , then the handling
fee is $?— ppd., and I’ll provide a manila envelope.

ZEROMATIC™ TUNING
CONTROL for
PRO-2004/5/6
By Gregory K. Doerschler

ED: The term “Zeromatic” used in
Greg's article is a trademark by the
Tandy Corporation.

The Realistic PRO-2006 scanner
incorporates " Zeromatic tuning " in the
Search mode. When a signal is
detected, Zeromatic keeps Search from
stopping prematurely on an adjacent
frequency by holding the SQuelch
closed until the signal is center tuned.
With a simple mod, the Zeromatic
tuning circuit can be activated in Scan
and Manual modes as well. In these

modes, the circuit can SQuelch splatter
from strong adjacent channel signals as
well as any images or stray signals that
are more than a few kHz off-frequency.

The idea for this mod came as a result of
my search for elusive low power signals
on 12.5 kHz “split”" channels in the
461465 MHz band. With the PRO-2006,
there is no way to Search these freqs
without hitting the standard 25 kHz¬
spaced business channels as well. (For
instance, you can't Search 461.1125 and
461.1375 MHz without also hitting
461.125 MHz.) Activity on the 25 kHz
channels was so heavy that I missed most
of the elusive stuff on the split freqs.

When I installed the 6400 channel
memory mod in my 2006, I decided to
program all of the 461465 MHz split
freq allocations in dedicated memory
banks so I could Scan them exclusively,
rather than use the Search function.
The problem with this plan was that
adjacent channel splatter from very
strong signals on the standard 25 kHz
channels would often lock up the Scan.
Realizing that adjacent channel splatter
did not cause problems in the Search
mode because of the Zeromatic tuning
circuit (which holds the SQuelch closed
until the Search stops on the actual
transmission frequency), I surmised that
activating the Zeromatic circuit in the
Scan and Manual modes would also
keep adjacent channel signals from
breaking SQuelch in these modes.

IC4 on the main PC board of the 2006 is
at the heart of the Zeromatic circuit.
When the frequency error of an
incoming signal exceeds the Zeromatic' s
tolerance, a high output will be present
at either pin 7 or 8 of IC4. In the Search
mode, this output is fed to pins 5 and 6
of IC3 (which functions as an inverter);
producing a low output at pin 4. This
output and the receiver SQuelch gate
output at IC2 pin 13 are fed to pins 2 and
1 of IC3 (a NAND gate) respectively.

The output of this NAND gate (pin 3) is
the SQuelch signal which is sent to the
CPU via the "SQ" line at pin 5 of CN3.
A low output means an open SQuelch,
and the CPU stops the Search. Since
this output will be low only when both
inputs (pins 1 & 2 of IC3) are high, the
Search will not stop unless (A) a high
input at pin 1 is present due to an open
receiver SQuelch and (B) a high input at

4/24/95- 1:47PM- The “WorldScanner Report’ 9 © 1991-95; Volume 5, No 4; Page 6

pin 2 is present, which occurs when the
incoming signal is tuned within the
Zeromatic circuit's frequency tolerance.

The frequency tolerance of the Zeromatic
circuit varies depending upon the Search
step. When SEARCHing in 5 kHz steps,
+5 volts is supplied by the CPU on the
5kHz line, which runs to the Zeromatic
circuit via CN3 pin 7. This results in a
tighter frequency tolerance when
SEARCHing in 5 kHz steps than when
SEARCHing in 12.5 or 50 kHz steps.
(This makes sense since your closest step
will always be within 2.5 kHz of the
actual frequency when SEARCHing in 5
kHz steps, but may be as much as 6.25
kHz off frequency when SEARCHing in

12.5 kHz steps.) For the remainder of
this article, I will refer to these two
frequency tolerance settings as the
Zeromatic "narrow" and "wide" settings.

When the scanner is not in the Search
mode, the Zeromatic outputs at IC4 pins
7 & 8 are diverted to ground via IC3 pin
10, effectively disabling the Zeromatic
circuit. IC3 pin 10 is the output of an
inverter, which receives its input signal
on pins 8 & 9 from the CPU via the
"SEARCH" line (CN3 pin 6). The CPU
supplies +5 volts on the SEARCH line
whenever the scanner is not in the
Search mode. It is this signal that turns
off the Zeromatic circuit.

There are several ways the 2006 can be
modified to activate the Zeromatic circuit
in the Scan and Manual modes. The
circuit can be used in the wide setting or
the narrow setting, or made switchable
between the two. A switch which turns
the circuit off entirely may also be added
for those times when you'd want to be
able to hear off-frequency signals (such
as when you're trying to identify them).

The wide and narrow Zeromatic settings
do a comparable job of SQuELCHing
adjacent channel transmissions, but the
narrow setting does a better job of
SQuELCHing images and other
interfering signals which are only
slightly off freq. For instance, I find that
it effectively SQuelchcs many of the
cellular telephone images which I receive
in the aircraft band when they do not fall
directly on the programmed frequency.

The disadvantage of the narrow setting is
that some desired transmissions could
also be SQuELCHed if they are a bit off-
frequency or if the scanner is not

programmed to the exact transmit
frequency. This could especially be a
problem for scanners that are subject to
temperature extremes (such as in a
mobile environment) where the internal
oscillators would be more apt to have
shifted somewhat over time. Using the
narrow Zeromatic setting, a signal only

1.5 kHz off frequency would not be heard
if the scanner's oscillator had also drifted

1.5 kHz in the opposite direction. The
wide Zeromatic setting is sufficiently
forgiving for this not to be a concern. I
use the narrow Zeromatic setting
exclusively in my 2006 and have not
encountered any problems, but it is
important to be aware of the potential.

To measure the tolerance of the two
Zeromatic settings, I swept a strong,
unmodulated carrier across the scanner's
programmed frequency with Zeromatic
tuning in the narrow, wide and off
settings (using the NFM mode). The
carrier broke SQuelch over a range of
approximately ±2.8 kHz with the narrow
Zeromatic setting, ±5.1 kHz with the
wide Zeromatic setting, and ±9.0 kHz
with the Zeromatic tuning turned off. A
modulated carrier takes on a "fuzzy,"
chopped-up sound if centered exactly on
the Zeromatic tuning's tolerance limit,
and disappears altogether quite abruptly
when centered just beyond the limit.
With the Zeromatic tuning turned off, a
modulated carrier would produce splatter
on voice peaks when centered beyond the
±9.0 kHz limit (as previously discussed).

The easiest form of this mod is to hard¬
wire the Zeromatic tuning circuit to be
operational full-time in the wide setting.
Clip the brown wire from CN3 Pin 6 on
the main board about midway, and
connect the CN3 side to ground through
a 10K resistor. (CN3 is a 15-pin
connector located on the front edge of
the main PC board.) If you have the Key
Research PS-90 “Search & store” mod
in your scanner, you will have to remove
the white wire connected to IC-3 pin 8
and reconnect it to the clipped brown
"SEARCH" wire running to the CPU
board.

Figure 1 illustrates how to make this
mod switchable using a SPDT switch.
Note that the Zeromatic function will
continue to operate in the Search mode
regardless of the position of the switch,
and will still revert to the narrow setting
when SEARCHing in 5 kHz steps.

To activate the narrow Zeromatic setting,
perform the above wide Zeromatic mod
(preferably with the switch). Install a
NPN switching transistor (2N2222A) as
shown in Fig-2. D47 is on the main PC
board behind CN3. The cathode is the
top lead. If you're good at working in
relatively tight places, solder the emitter
of the transistor directly to D47 and
solder the collector of the transistor to
the pad on the PC board directly behind
CN3 pin 3; next to D47. This is a source
of +5 volts. Other accessible sources of
+5 volts include the output (rear-most
lead) of voltage regulator IC8 on the left
edge of the main PC board, and IC3 pin
14 on the main board.

The base lead of the transistor gets wired
to the center pin of your SPDT
"wide/narrow" switch. If you only want
the Narrow Zeromatic setting without
the ability to switch to Wide, omit the
switch and 10K resistor and connect the
transistor's base directly to the clipped
brown SEARCH wire leading to the CPU
board. I consider this switch to be a bit
frivolous as long as you have the
Zeromatic on/off switch, but it is your
choice if you want to include it When
the scanner is used in the Search mode,
the NPN transistor is turned off and the
wide/narrow Zeromatic selection is
determined by Search step. Neither the
Zeromatic on/off switch nor the
wide/narrow switch will affect the
Search mode.

I installed a DPDT switch for the
Zeromatic "on/off" switch in my 2006
instead of a SPDT switch, and used the

4/24/95-1:52 pm~ The " World Scanner Report” © 1991-95; Volume 5, No 4; Page 1

NOTE: This is a simplified diagram of
I the PRO-2006 Zeromatic circuit that
really requires benefit of the Service
Manual for full understanding. Do not
| fail to acquire one for your scanner.
There are minor differences among the
PRO-2004/5/6/2035 (800)442-2425

PRO-2006 ZEROMATIC CIRCUIT

-O R#d ^ SQuvIch

> To CN3 Pin 6
(Set Figure 3)

second set of switch contacts to engage
a manual tuning mod. This was
accomplished by clipping the red SQ
wire running from the CPU board to
CN3 pin 5 midway and splicing in the
switch as shown in Figure 3.
Essentially, when I turn off my
Zeromatic tuning, this second set of
switch contacts sends an "open
SQuelch" signal to the CPU; regardless
of whether a signal has actually broken
the SQuelch. This prevents the scanner
from SEARcmng or scanning since it
thinks it’s hearing a signal. I can then
enter a frequency into any channel, push
the DIRECT key, and use the
UP/DOWN keys to manually tune up or
down from the frequency I entered;
similar to a tuning knob. This is the
one time when I definitely want
Zeromatic turned off in order to hear
off-freq signals as I approach them.

The manual tuning mod can also be
performed or controlled independently
of the Zeromatic tuning mod.
Combining the two on a single switch
was a practical consideration for me.
With ten toggle switches and two jacks
I'd already added to the back of my 2006,
available real estate was getting pretty
scarce!

FIGURE 3

Red "SQ” Wire

To CPU Board

0 — i
“0 -> _

Switch shown in

Manual Tuning Off
Zeromatic "On"

Red "SQ" Wire

ToCN-3, Pin 5

Position

To test the Zeromatic mod, find a very
strong local signal and punch in a
frequency 10 kHz away from it (or 5 kHz
away, if you're using the narrow
Zeromatic setting). Open the SQuelch
by turning the SQuelch control fully
counterclockwise. Whenever the strong
local signal transmits, the SQuelch
should close; silencing the speaker.
With the Zeromatic tuning turned off,
you should hear splatter from the signal.

You can actually demonstrate this effect
without even performing the mod. Enter
a frequency 10 kHz away from a strong
local signal, on which you can hear
splatter when the local signal transmits.
Then enter that frequency as both an
upper and lower Search limit and go
into the Search mode. The Search

range will be limited to just the one
frequency and the Zeromatic tuning will
be on, so the splatter will not be heard.

I do not believe that there are any
negative side-effects to the Zeromatic
mod. If you encounter an off-freq or
adjacent channel signal while scanning
with Zeromatic engaged, the Scan may
sometimes pause silently for an instant
on either the affected channel or the next
channel in the Scan sequence. Without
the Zeromatic tuning though, the Scan
would stop and you'd be listening to the
interfering signal; so it's really not an
annoyance by comparison.

Those who have performed the automatic
tape recorder switch Mod-33 or the
carrier indicator mod from Vol-2 of the
Scanner Modification Handbook may
notice the relay or LED indicator
momentarily click "on" even though
audio is not present and the Scan does
not stop. This is due to the fact that these
mods take their SQuelch signal directly
from the receiver SQuelch gate at IC2,
and they will sense when an off-
frequency signal breaks the SQuelch
even though the Zeromatic tuning
prevents the open SQuelch signal from
being sent to the CPU.

Understand that Zeromatic does not
actually improve the selectivity of the
scanner. Offending off-freq or adjacent
channel signals are "ignored" by the

scanner, but they are still present in the
circuit and could mask weaker, desired
signals. Nevertheless, my Zeromatic
Mod allows channels to be scanned that
otherwise would probably be locked out
because of interference. ©

ED COMMENT: Greg did a hell of a
job on this article; my hat’s off to ‘im!
Wish I had developed it myself Well I
get to help anyway. Greg didn’t have
the resources to identify the differences
among the PRO-2006, PRO-2005, and
PRO-2004, so follows my list of those
differences. This Zeromatic Mod will
work with these three scanners and
maybe others with similar Zeromatic
tuning circuits. The PRO-2035 differs
enough that an altered procedure will be
covered in a future article . A quick
exam of the PRO-43 reveals a Zeromatic
circuit similar to the PRO-2035 *s so stay
tuned for more. Perhaps Greg and I can
work up the mods for other Realistic
scanners, too. Sorry, Uniden scanners
are much too different for this mod.

PRO-2006

Squelch:

CN-3 Pin 5

Search:

CN-3 Pin 6

5 kHz Step:

CN-3 Pin 7

PRO-2005:

Squelch:

CN-3 Pin 5

Search:

CN-3 Pin 6

5 kHz Step:

CN-3 Pin 7

PRO-2004:

Squelch:

CN-504 Pin9

Search:

CN-504 Pin 10

5 kHz Step:

CN-504 Pin 14

4/24/95-1:54 PM ~ The “ World Scanner Report” © 1991-95; Volume 5, No 4; Page 8

FROM THE READERS

From: Burleson D. White, Beachwood, OH

Are you planning to review the AOR AR-
8000 AR-8000? Is it modifiable? Why not
use the CE-232 computer monitor screen to
replace the dead PRO-2004/5/6 EL display?

ED : AOR scanner series are marketed by a
firm that does not cooperate with or respond
to our requests for technical information.
Furthermore, AR Service Manuals suck
rocks. On that basis, I do not buy AR
scanners and therefore never have one in
hand to review unless someone gives or loans
me one. So far, that hasn ’t happened.

The CE-232 certainly offers a superior
display to that of any scanner, but it is rather
expensive for a “ replacement © By the
way, the EL panel in these scanners is a
backlighting panel; not the actual LCD
display module. I have never seen a display
fail unless it was physically broken. The EL
panel slides behind the Display module.

From: William Shaft. Tinlev Park, IL

Doc, Doc: Send me the news. Willie Shaft
here has a new PRO-2035 and needs the
Ultimate Scanner to find out what to do. I
have Scanner Mod’s Vol 1 & 2 and have
hacked the PRO-2004/5/6 and the PRO-34.

The PRO-2004 will always be my favorite
because of the nice angle, touch keyboard
and metal case. Thanks for the advice
warning that the Tandy dorks make parts not
available for the PRO-2004. Until I see your
book, the solder sucker and iron will stay
ready. P.S. I love listening to all the Adam
Henry’s with car phones. Wireless shouldn’t
be private.

ED : The PRO-2035 proves hackable, along
the lines of the PRO-2004/5/6, since it is
much the same scanner, electrically. The
Ultimate Scanner offers a good start and the
WSR will continue its enhancement and
development. I agree that it’s downright
ignorant of Congress to legislate privacy of
the airwaves. That’s no different than
legislating privacy of conversations in
restaurants, workplaces, public parks, and
on the sidewalks! Good grief!

From: Arthur Zepeda. Visalia. CA Dear
Bill, I’m not much for writing letters, but
you’ve got to read my story. I’m going on 28
years of age. I have a high school diploma
and also an A.S. Degree in automotive repair.
I’m currently going on six years working for
the school district in Visalia and about one
year as a night lead custodian (janitor, for
those who work for the government. HA!).
Prior to that, I spent four years in the Army as
a Chaparral missile crewman. Aside from
Basic and ATT, I was stationed at Ft Ord the
whole time.

So where is my electronic experience you
might ask? There really isn’t any. Aside
from the electronic aspect of a car, they just
teach you to find and repair.

So, I have a PRO-2006/43/51 and a 22. No,
not caliber, an old 6-ch crystal (yard sale $5).
A lot of $$$ plus $25 to have someone
“install” cellular frequencies. Hmmm. When
I purchased the PRO-43 (first scanner), oh,
by the way, I just didn’t start off with the 43,
but that’s another story. Anyway, not even in
my wildest dreams did I ever think I would
open and do the cell mod to the 43! I’ve
never even used a soldering gun on those

delicate electronic components! Then.I

saw your two books in a Grove catalog. “I’ve
got to have those,” I said to myself.

I was visiting some friends in San Carlos,
CA, and we went to a shop called “ Scanners
Unlimited.” Cool shop, by the way. Nothing
like it where I’m from (40 miles south of
Fresno). I purchased Book 2, and was amazed
at how simple y ou made everything seem.

I started with the C.O.I., Mod 32 on the
2006, and you betcha, I was proud. Next
came Mods 26 & 27. Big head now! Then
came the WSR, Book 1 and back issues of the
WSR. That’s when the 43 went on the
operating table for the cell mod. This, of
course, was my first job dealing with SMT.
Wow! My eyes still hurt!

And, just as I’m writing this letter, UPS lias
just delivered the stuff for the 25,600 channel
and mod 28 from JDR Microdevices!!!!

The bottom line is this. Thank you Bill for
making it easy for me to add another
dimension to my monitoring hobby! I look
forward to adding your third book to my
library! Try to keep up the good work. I
realize it’s getting harder to hack because of
firmware but you can deal with it. Take care
and God bless you and your family! PS I
actually paid someone to clip two diodes on
the 2006! Man!

ED : Thanks for your story. I often wonder
how people get started. There were many
turning points in my life starting with a
transistor radio for my 12th birthday in
1957. 1 opened the back of the case and

poked around on the solder joints with the
end of a 100-ft longwire. Suddenly stations
roared in, including HCJB in Quito,
Ecuador, with an Armed Forces Day
program. Hooked! Some years later, 1 got
ripped for a $50 repair bill on a funky old
CB radio. That got me started on working on
my own stuff. The FCC busted me in 1987
which started me in earnest on scanners. The
rest is history. Do keep us posted!

4/24/95~2:oo pm ~ The “World Scanner Report” © 1991-95Volume 5, No 4; Page 9

1 iiSiii^iSiiiiiSi^S

NAME:

USA RATES shown: Canada add 15%: Other Foreign +25%-surt/+50%-Air

$

STREET

1991 (1st Year, Jan-Nov/Dec) - lOea $20.00

$

1992 (2nd Year, Jan-Nov/Dec) - 10 ea $21.00

$

CITY: STATE: ZIP:

1993 (3rd Year, Jan-Nov/Dec) - 10 ea $23.00

1994 (4th Year, Jan-Nov/Dec) - 10 ea $25.00

$

s

Work Ph: ( ) - Career or

$

Home Ph:( ) - Profession

1mm •

TYPE OF SCANNERS »

& Other Radios »

Half Year 5 ea $15.00

One Year lOea $25.00

METHOD OF Check Cash M.O. Visa MstCard COD (+$8.50)
payiuifnt » n n n n n

Amount Enclosed

&

Two Years 20 ea $45.00

Credit Card

Acc't No: » -

Amount Charged
$

Scanner Mod Hndbk, VoM : $17.95 + $4.00 S&H *
Scanner Mod Hndbk, Vol-2: $17.95 + $4.00 S&H *

Name of Expiration /

Ultimate Scanner til 6/30/95 $24.95 +$4 S&H *
Scanners & Secret Frequencies $19.95 + $4 S&H *

Issuing Bank Date:

i

Signature Required (for credit card purchases)

y

|( |

* Canada USS7 S&H; Other Foreign US$9 S&H; Air extra

CE-232 Interface Kit $194.95 + $5 S&H: All Foreign add 25%-surf

VISA !|

.. 1

Calif reaidenta: Sale* Tax - 7.0% on all orders except WSR subs

What else to tell us?

r ^pi

I Master

TOTAL THIS ORDER?—»

From: Paul Longo, Stamford, CT Your
observations in V5N3 of the WSR are, as usual, right
on the mark. It seems that form has superseded
function in everything. How many restaurants have
you gone to in which you find opulent decor,
mediocre food and lousy service? Looks like the
yuppies put more value on how things (or people)
look rather than how well they work. The “empty
shell syndrome” creeping into new scanners is a spin¬
off of the “empty suit syndrome” that now runs
rampant in corporate America. (When are we going
to lose these people,?)

ED : We’re not, Paul. Look back 500-yrs and see
how “backward” people were? Well 500-yrs from
now, they’ll be looking back and chuckling at how
backward we were. But us Hackers will be their
revered ancestorsI

NiCd & NMH BATTERY SOURCE

From: Tony Thornton, Mize, MS Bill, do you
know of a source for NMH batteries with a better
price than the $7.00 each that Metro West wants for
them. I’ve looked in various catalogs such as “Digi
Key” and others, but haven’t found any listed. I’ve
seen the mfgr’s ads in a couple of trade magazines,
but found no source but Metro West. I’ll pay the
$7.00 if I have to but would like to think they’re
available cheaper than that Keep up the good work.
(Can a NI cad charger be used with them?).thanks.

ED : A recharger is a recharger, but designs must
be optimized, else you ’ll overcharge or
undercharge. I’ll do an article on the subject soon,
since that’s an important topic. You can check the
following company, but I have no clue on their
prices. Tell ’em we sent ya.

Alexander Battery Co; PO Box 28880,
San Diego, CA 92198; (800) 327-0814

displayed. “PRIVATE” calls don’t get answered here.
Also, certain social agencies have an automatic Caller
ID block on their phones (places like battered
women’s shelters, etc).

PRO-43 DISCRIMINATOR OUTPUT

Now I have just one question for you. Where is the
discriminator point on the PRO-43 radio? I want to
run a line from there to a jack, so I can plug in a
PL/DPL reader into it, and I need the point where the
signal can be picked off before it is stripped in the low
pass filter. If you have time, could you post it to me
in the Internet at DARYLLI@AOL.COM. Thanks!
I’ll be waiting for your new book.

PRO-43 AF BOARD (TOP)

If I were you, I’d solder a 2.2-pF/16v capacitor, (+)
lead to Pin 9 or TP-201 and take your output ojf the
(-) lead. That will protect the chip and still pass
plenty of signal to your PL device. Remove the rear
case of the PRO-43 and you should see Pin 9
staring up at you as shown in the graphic.

Thanks for the added info on Caller W. I don’t
know much about it yet since Calif doesn ’t allow us
to have it. The Ultimate Scanner looks to be
available on or about May 1, now so hang loosef

VOTE ON MY NEXT BOOK

MORiONeALlilRID

From: Darvll Symington, Holland, OH I n the last
WSR, there was a discussion on Caller ID. In Ohio,
Caller ID will not transmit the number of any phone
subscriber that already has an unlisted number. Only
“PRIVATE” will show. Ail callers can block Caller
ID by dialing *67 before each call. That way, the
caller can choose if he/she wants their number

ED : How about both ways, here and via the
Internet? This way helps others, too. I’ll even draw
ya a picture so there can be no mistake. The
discriminator chip differs little from one scanner to
the next, though the chip numbers, pin counts, and
styles may very widely. In the PRO-43, it’s IC-301,
Pin 9, a TK-10427 or TK-10420 surface-mount
chip. Pin-9 is also TP-301, one and the same point.

Hey guys ‘n gals, I need your help for my
next book. The Ultimate Scanner opens
doors for endless opportunity to write, but
what do I wile about next? My publisher
and I are considering a series of detailed,
moderately priced manuals, each dedicated to
one particular scanner with a boatload of
mods & hacks just for that rig.

Ok, so which do I do first? Second? Third?
Why don’t YOU dear WSR readers vote to
give me a sense of direction for the first ones.
Then, I’ll let the buyers of the series vote on
subsequent works. OK, here is what I want
you to do: Use whatever is best for you: US
mail, fax, e-mail, CompuServe, BBS, or even
voice phone....just tell me your first three
choices of make and model of scanner for me
to write about. Please write “ VOTE 9 on the
outside of envelopes, or on the subject line of
e-mail, fax, and BBS messages. List your top
three picks in order. There is no deadline,
but the sooner, the better, for obvious
reasons. I’ll compile results and make a
tentative decision by July 1 and maybe start
work in earnest in August.

My e-mail, CIS-Compuserve, BBS, Fax, and
phone info are in the Reference Information
box at the top of Page 1. Drop me a line with
your guidance for my next book, oo

CHECK YOUR EXPIRATION DATE

04/23/95-23:30- The “World Scanner Report” © 1991-95; Volume 5, No 4; Page 10

♦

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Check Your Expiration Date on the Mail Label Below!

iissji^a$i^240

+ Subscription Rates Going Up ~ Ultimate Scanner book still a great bargain
+ Contest last month doing great ~ Some Subscriptions Soon to Expire
+ PRO-2004/5/6/2035 Receiver Circuits Explained ~ Mixers, IFs, NFM/AM
+ Zeromatic Tuning Control for PRO-2004/5/6 ~ A Feature Mod!

+ Need a clean set of schematics for your PRO-2006?

+ Why we don’t mess with AOR Scanners ~ EL Panel tidbits
+ PRO-2035 Hack Future ~ A new hacker’s story: Arthur Zepeda
+ Editor’s historical brief ~ “Empty Shell Syndrome”

+ NiCd & NMH battery source ~ More on Caller I.D.

+ PRO-43 Discriminator Output ~ VOTE on my next book(s)